All Commands / Tile Taps suddenly result in "Error" or "Not Authorized"

The toast message may say "Error:" or "This request is not authorized by the specified Access Token".

Unless this is a temporary system-wide or SmartThings Platform issue, the following may help:

This error may be resolved by just "re-authorizing" your Location(s):

1. Go to https://app.actiontiles.com/locations and select your Location; then select "Location Settings" (upper right corner ... menu). Then select "Authorize Things".
2. Go through the SmartThings Authorize process again. It should not hurt anything and likely will reset the SmartThings Access Token